1. Field of the Invention
The present invention relates to a method for selective dealkylation of alkyl-substituted C9+ aromatic compounds using a bimodal porous dealkylation catalyst at a low temperature, and more specifically to a method for selectively dealkylating alkyl-substituted C9+ aromatic compounds at a low temperature by the use of a dealkylation catalyst that has a bimodal porous structure including both mesopores and micropores and includes a crystalline aluminosilicate and a metal.
2. Description of the Related Art
C9+ aromatic compounds are produced as by-products of petrochemical processing. Specifically, such C9+ aromatic compounds are produced in the entire petrochemical processes, including naphtha reforming processes, benzene, toluene and xylene (hereinafter referred to simply as ‘BTX’) production processes and para-xylene production processes, which use crude oil as a starting material.
Particularly, para-xylene is produced via isomerization of C8 aromatics. In this process, disproportionation and transalkylation of xylenes and ethylbenzene occur as side reactions. These side reactions produce ‘alkyl-substituted C9+ aromatic compounds,’ such as ethyltoluenes, trimethylbenzenes, ethylxylenes and diethylbenzenes. Since most of the by-products are of little practical value, they are used as fuels without further processing or are used, together with toluene, as raw materials in conversion processes to BTX, such as TatoraySM, TransPlusSM and TAC-9, using mordenite-based catalysts.
There is a strong need to recover trimethylbenzenes as C9+ aromatic compounds that are widely used in various industrial fields. Specifically, 1,3,5-trimethylbenzene (mesitylene) and 1,2,4-trimethylbenzene (pseudocumene) are used as solvents of resins, gums, nitrocelluloses, etc., raw materials for lacquers, paints and varnishes, and components of chemical products including antioxidants. In the electronics industry, mesitylene has also been used as a developer for photopatternable silicones due to its solvent properties.
Many mesitylene production methods are known and include, for example, bringing acetone in the liquid phase into contact with sulfuric acid and a catalyst (see U.S. Pat. No. 3,267,165) and bringing acetone in the vapor phase into contact with a catalyst (see U.S. Pat. No. 5,087,781). However, these methods have disadvantages of low conversion of acetone, low mesitylene selectivity, waste water production and complicated processes.
Many methods for producing mesitylene from C9+ aromatic compounds are also known in which ethyltoluenes having a boiling point similar to that of mesitylene are first converted to BTX using a catalyst, followed by extraction in a distillation column. Examples of such methods include a process for the production of mesitylene through isomerization of pseudocumene using ZSM-5, a zeolite catalyst (see U.S. Pat. No. 7,157,397) and a production process in which C9+ aromatic compounds produced during petrochemical processing are further treated with a metal-supported ZSM-6 catalyst, which is a kind of zeolite catalyst, followed by separation into mesitylene and pseudocumene in a distillation column (see U.S. Pat. Nos. 5,004,854 and 4,320,242). However, such methods have disadvantages in that the conversions are low due to the shape selectivity of the catalysts for the reactants and the high reaction temperatures lead to low recovery yields of mesitylene.